Preparation of a conformable nonwoven web



United States Patent Ofi'ice 3,259,539 Patented July 5,, 1966 3,259,539 PREPARATION OF A CONFORMABLE NONWOVEN WEB Manfred Katz and Munzer Makansi, Wilmington, Del., assignors to E. l. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 28, 1963, Ser. No. 319,582 14 Claims. 7 (Cl. 162-146) This application is a continuation-in-part of our application Serial No. 27,476 now U.S. Patent No. 3,117,056

of January 7, 1964.

This invention relates to fabrics and more specifically to novel nonwoven fabrics prepared from synthetic organic polymer fibers.

Fabrics in general fall into two classes: woven and nonwoven. Woven fabrics usually include knitted fabrics and may be defined as fabrics formed by the interlacing in a predetermined regular geometrical pattern of one or more long lengths of yarns or filaments. Nonwoven fabrics, on the other hand, are usually formed by a random or controlled deposition of filamentary strands to form a sheet or batt followed by binding these strands in some way to provide strength and dimensional stability.

Although each type of fabric has advantages for applications in specific areas, there are certain fundamental property difierences whichhave hitherto been considered as inescapable adjuncts of the method by which the fabric was formed. Woven and knit-ted fabrics have generally been recognized as stronger, more flexible, more readily prepared in light weights, and more drapable. Nonwoven fabrics, such as felts, have, for the most part, been confined to applications such as hats, filter cloths, and so on, because of the ease with which they can be formed into a dense material of low porosity and also because of the low cost of preparing the finished fabric structure directly from the individual fibers.

The advantage of low processing cost is one of the very desirable features of nonwoven fabrics. All of the various processing steps which are required in the preparation of woven and knitted fabrics add considerably to the cost of the final product. Thus, in the formation of a woolen suiting material, the wool fibers must be formed into a yarn, the yarn must be twisted or plied and the resulting final yarn product must then be woven into a fabric. It would be extremely desirable to provide a process which would involve simple well-known papermaking procedures or other known techniques for making nonwoven structures but would produce a textile fabric having the properties of a woven fabric.

Although low cost and certain property advantages of nonwoven fabrics have led to the employment of these materials in a number of specific end uses, limitations which have hitherto been considered a necessary part of the nonwoven structure have eliminated them from many apparel applications. Womens skirts are occasionally made from certain nonwoven felts, but in general these have enjoyed very limited appeal. It has not been found practical to make Women's dresses, mens and Women's sui-tings, coatings, sweaters, and the like from nonwoven fabrics, one of the major reasons being that nonwoven fabrics have heretofore been rather stilf and bulky and, therefore, possessed poor drapability.

Nonwoven fabrics could find extended utility if ways could be found to alter their dimensions and thickness after formation in a controllable and permanent manner.

Fabrics having such properties would permit the manufacture of apparel which could be shaped or molded to the body of the user. Moreover, if the thickness dimension of such fabrics could be increased without shrinkage of the lateral dimensions even greater versatility would be afforded the fabric. Furthermore, if fabrics of such a conformable and bulkable nature were available, they could be employed in many non-apparel uses such as upholstery, home furnishings, and even many industrial uses as fabric-covering materials for rigid three-dimensional articles, where the conformability would avoid or at least reduce the need to fold, pleat, tuck and otherwise shape an essentially fiat material in conformity with a three-dimensional curved surface.

Some fabrics, such as wool, can be made to retract under certain conditions. Woolen clothes, for example, are shaped into conformity with the human body with the use of steam irons, etc., but this shapeability is of very limited nature. Furthermore, the change in dimension is in one direction only; that is, the fabrics can be shrunk but they cannot be caused to expand to any appreciable extent. Shrinkable synthetic fibers' are also 'known, but up to now there has not been available any nonwoven synthetic fabric which was extensible, bulkable, and conformable.

It is an object of this invention to provide a process for the production of nonwoven synthetic fabrics which exhibit a combination of flexibility, strength and a conformable, bulkable, extensible nature in response to simple thermal treatment, thereby affording fabric-s which can be shaped as desired to con-form to three-dimensional contours.

A further object is to provide a process for the production of nonwoven bonded fabrics of synthetic fibers, which fabrics exhibit a combination of high-tensile strength, conformance, bulk and high drape thereby affording aesthetic and physical properties comparable to those of woven or knitted textile fabrics of' the same weight and fiber composition.

It is also an object of this invention to provide nonwoven fabrics of synthetic fibers by a novel process using conventional paper-making techniques and equipment.

The products of this invention are conformable, bulkable nonwoven fabrics of synthetic fibers comprising at least 50% by weight of synthetic organic spontaneously elongata'ble fibers, as defined in detail below, together with from 3% to 50% by weight of a synthetic organic polymer binder dispersed uniformly throughout the non woven web, said binder having a modulus (Mi) between about 0.002 and about 25 grams per denier (g.p.d.). Certain of the nonwoven webs prepared by the process of this invention have the capacity upon heating to form a bonded nonwoven fabric in which the fibers contain at least 30 crimps/inch (c.p.i.) and in which the fibers are bonded at spaced points throughout the fabric such that the average total length of an individual fiber element between adjacent fiber bond points is at least 1.25 times the straight line distance between the same fiber bond points. The binder is present in an amount such that percent binder X3v'lVli of binder 40 pension of synthetic organic spontaneously elongatable staple fibers and a synthetic organic binder. in water, the suspension containing less than about 10% solids. by weight and preferably less than 5%. By the term "spontaneously elongatable fibers is meant fibers which are capable of elongating spontaneously at least 3% upon heating at a temperature 30 C. above the second order transition temperature of the fibers for five minutes. A waterleaf is prepared from the slurry and dried at a temperature below that at which the fibers elongate spontaneously and also below the fusing temperature of the binder. The waterleaf is then heated at a temperature sufiicient to fuse the binder and also to elongate the fibers at least 3%, based on their original length, while restraining the fabric from increasing more than 3% in linear growth in any surface direction. Of course, a liquid other than water may be used as the suspending medium for the fibers and binder so long as it is inert to the solids, but economy and convenience favor water as the liquid phase. Also greater concentrations of solids may be employed, say up to or more, but the most useful sheets are obtained with 5% solids or less.

In another embodiment of the invention, webs containing spontaneously elongatable fibers in the form of I continuous filaments are prepared by processes employing electrostatic phenomena to control the formation of the nonwoven structure, as described in Belgian Patent 608,646 granted October 13, 1961, whereby the filaments, relaxed during or after web formation, are thereafter capable of spontaneous elongation upon heating. The binder can be incorporated into these nonwoven webs by any of the standard methods known in the art. Thus, the binder may be applied as asolution or an aqueous dispersion. Usually the volatile carrier for the binder is then removed, prior to the actual bonding step, by heating at atemperature low enough to avoid spontaneous elongation by the fibers. The web is bonded by heating under restraint to elongate the fibers and fuse the binder. The binder can also be applied by sifting it, in finely divided form, onto the web. The binder in the form of fibrids or as staple fibers can be laid down in the Web concurrently with the elongatable fiber by flowing an air stream carrying the binder into the air stream used to forward the electrostatically charged filaments toward the web laydown zone. An especially effective method for distributing the binder throughout the web involves cospinning the binder in the form of continuous filaments which are deposited along with the main elongatable fiber constituent of the web.

Carding machines, Rando-Webber machines and other equivalent devices can also be used to prepare the nonwoven webs to be treated according to the process of this inilention.

The individual filamentary components of the fabrics prepared by the process of this invention possess a high degree of lateral freedom and flexibility in three dimensions between intersection points and points of bonding, thereby providing certain of these fabrics with a high degree of drape and softness, high tensile strength, low bulk and a soft handle in the same range as woven fabrics. These fabrics are characterized by a fabric density of 0.28 to 0.6 g./cc., a drape stiffness of not over 1.0 inch, a ratio of tensile strength to drape stiffness of at least 12.0 lbs., and a sonic velocity-elongation differential of at least 1.3. They are, therefore, readily distinguished from papers on the one hand and conventional thick and bulky nonwoven felts on the other. The novel nonwoven fabrics of the process of this invention are equivalent in handle, thickness, drapability, strength and other aesthetic and physical properties to a wide spectrum of woven fabrics. The process of this invention can also be utilized to confer excellent conformability and nonpapery character to nonwoven fabrics which do not have the above-mentioned characteristics of softness and drapability because the crimp level in the constitueit fibers, the binder content, or the fabric density does not lie within the necessary limits. Such fabrics are, however, of value in applications where a certain degree of stiffness is desirable, e.g., .n the fabric interliners and tents, because of their conformability and nonpapery character which derive from the use of spontaneously elongatable fibers.

Conformability may be defined as the ability of a material to be shaped to a three-dimensional surface when stretched thereover and can be expressed quantitatively as the area of the material which conforms to the surface of a sphere (e.g., 3" in diameter) Without breaks or folds. A soft, drapable fabric prepared by the process of this invention will, merely under its own weight, conform over a significant area of the surface, while other fabrics prepared by the process of this invention will exhibit good conformability when added weights are attached to the edges of the fabric.

Nonpapery character which is also obtained in the fabrics prepared by the process of this invention is evidenced by the lack of or low level of noise of various frequencies which is generated when the fabric is flexed. A quantitative measurement of this can be made by analyzing the sound produced under uniform flexing conditions. Nonpapery character is also shown by the lack of sharp bends in the fabric when subjected to the conformability test outlined above. Certain papers, e.g., soft cleaning tissues, may exhibit little noise generation but will exhibit a definite papery break in the conformability test. Nonpapery character in the products produced by the process of this invention is of importance in the use of the materials as fabric interliners. Noise generation is aesthetically annoying in such applications and moreover, a papery break would show through to the exterior of the lined article. Noise generation is also undesirable in materials which are used as tent fabrics.

Spontaneously elongatable fibers are disclosed in Belgian Patent 566,145 granted September 27, 1958. Synthetic organic fibers may be prepared capable of elongating spontaneously up to 30% or more under the above stated conditions. Particularly suitable for preparing spontaneously elongatable fibers are pol esters, such as poly(ethylene terephthalate), poly(hexah3 dro-p-xylyl ene terephthalate), and similar polymers of monomers prepared by reacting terephthalic acid with ethylene glycol or similar glycols. Polyamides are also useful for this purpose, particularly poly(p-xylylene azelaeamide). In addition to these, other spontaneously elongatable fibers include those composed of polyurethanes, acrylonitrile polymer fibers, and the like. Polyolefins such as polypropylene and other addition type polymers may also be used, but polyester fibers are the preferred spontaneously elongatable fibers used in this invention.

In addition to the spontaneously elongatable fiber and binder utilized in the process of this invention, minor amounts of other fibrous materials may also be employed although it is preferred that these be kept at a minimum in order to achieve the most desirable properties in the products produced. Thus, ordinary staple fibers of synthetic organic polymers such as any of the polyamides, polyesters, polyurethanes, acrylic fibers, and polyolefins mentioned above, and additionally cellulosic fibers such as rayon, cellulose acetate, and the like may be used in minor famounts, preferably less than about 15% by weight based upon the dry weight of the web produced. In addition, certain natural fibers, such as goat hair, can be used in amounts up to 25% and preferably between 5% and 15%, to give fabrics of high resiliency.

In addition, of course, certain nonfibrous materials may be added to an extent not greater than 10% by weight of the final dry web to obtain a wide variety of particular product advantages such as color, surface properties, and the like.

Binders used in the process of this invention are synthetic organic polymers having an initial tensile modulus of between about 0.002 and about 25 grams per denier. The binder may be used in the form of a fibrid, which term designates a non-rigid, wholly synthetic polymeric particle capable of forming paper-like structures. Thus, to be designated a fibrid, a particle must possess an ability to form a waterleaf having a couched wet tenacity of at least about 0.002 gram per denier when a multitude of the said particles are deposited from a liquid suspension upon a screen, which waterleaf, when dried at a temperature below about 50 C., has a dry tenacity at least equal to its couched wet tenacity, and a capability, when a multitude of the said particles are deposited concomitantly with staple fibers from a liquid suspension upon a screen, to bond a substantial weight of the said fibers by physical .entwinement of the said particles with the said fibers to give a composite waterleaf with a wet tenacity of at least about 0.002 gram per denier. By a capability to bond a substantial weight of (staple) fibers is meant that at least 50% by weight of staple based on total staple and fibrids can be bonded from a concomitantly deposited mixture of staple and fibrids. In addition, fibrid particles have a Canadian freeness number between 90 and 790 and a high absorptive capacity for water, retaining at least 2.0 grams of water per gram of particle under a compression load of about 39 grams per square centimeter. Any normally solid wholly synthetic polymeric material may be employed in the production of fibrids. solid is meant that the material is non-fluid under normal room conditions.

It is believed that the fibrid characteristics recited above are a result of the combination of the morphology and non-rigid properties of the particle. The morphology is such that the particle is non-granular and has at least one dimension of very minor magnitude relative to its largest dimension, i.e., the fibrid particle is fiberlike or film-like. Usually, in any mass of fibrids, the individual fibrid particles are not identical in shape and may include both fiber-like and film-like structures. The non-rigid characteristic of the fibrid, which renders it extremely supple" in liquid suspension and which permits the physical entwinement described above, is presumably due to the presence of the minor dimension. Expressing this dimension in terms of denier, as determined in accordance with the fiber coarseness test described in Tappi 41, l75-7A, No. 6 (June), 1958, fibrids have a denier no greater than about 15.

Complete dimensions and ranges of dimensions of such heterogeneous and odd-shaped structures are diffi cult to express. Even screening classifications are not always completely satisfactory to define limitations upon size since at times the individual particles become entangled with one another or wrap around the wire meshes of the screen and thereby fail to pass through the screen. Such behavior is encountered particularly in the case of fibrids made from soft (i.e., initial modulus below 0.9) polymers. As a general rule, however, fibrid particles, when classified according to the Clark Classification Test (Tappi 33, 294-8, No. 6 [June] 1950) are retained to the extent of not over 10% on a lO-mesh screen, and retained to the extent of at least 90% on a 200-mesh screen.

Fibrid particles are usually frazzled, have a high specific surface area and, as indicated, a high absorptive capacity for water.

Preferred fibrids are those the waterleaves of which when dried for a period of twelve hours at a temperature below the stick temperature of the polymer from which they are made (i.e., the minimum temperature at which a sample of the polymer leaves a wet molten trail as it is stroked with a moderate pressure across the smooth surface of a heated block) have a tenacity of at least about 0.005 gram per denier.

Fibrid particles and their preparation are described in By normally 6 l ,V more detail in Belgian Patent 564,206. Fibrids can prepared from a number of polymeric compositions, a wide range of such fibrids can be used in the pres invention, leading to a spectrum of fabrics asindica above.

The web products of this invention contain jbetw about 50% and about 97% spontaneously elongate fiber and between about 3% to about 50% binder ba on dry weight of the web. Other fibers may be pres to provide special effects such as extra strength, d ability, etc., in amounts up to 40% but preferably l than 15% by weight of the web. Elastomeric bind useful in this invention (which are characterized byinitial modulus (Mi) of between about 0.002 and ab 0.9) should be used whenever a binder content grea than about 25% by weight is desired and then prefera in the form of fibrids. Binders having an intial modu greater than 0.9 should be used in quantities of less t1 about 25% based on the dry web weight. Obviously, procedure used for preparing these Webs may emp comparable quantities of fibers and binder since there usually no appreciable loss of solids during the PI'OCt In one embodiment of this invention, a waterleaf is p pared containing between 50% and 75% spontaneou elongatable staple fibers having a length of between and inch and from 25% to 5.0% elastomeric fibri In this embodiment, less than about 15% of ordinary h: fibers (nonelongatable) should be present. Represen tive elastomeric binders are the various butadiene-styrt copolymers containing from 30% to 70% combined bu diene, and also terpolymers of butadiene styrene, 2 acrylonitrile. Other preferred elastomeric binders inch a mixture of 98% polymethyl methacrylate plus 2% g cidyl methacrylate in the amount of 10 parts, andab 86 parts of an acrylate ester terpolymer; a mixture 49 parts polyhexylmethacrylate, 49 parts polyethyl ac late, and 2 parts polyacrylic acid prepared by solut polymerization, for example, in benzene using benz peroxide as initiator; poly(ethylene/propylene) polym ized using 3% dicumyl peroxide; a copolymer of an. phatic ester of acrylic acid and up to 5% acrylic at such as, for example, a copolymer of 98% ethyl acryl and 2% acrylic acid.' Another useful elastomeric bin is obtained by reacting poly(tetramethylene ether) gly of approximately 1000 molecular weight with tolylt 2,4-diisocyanate to give a glycol-terminated macroint mediate and this is treated to give an isocyanate-end low molecular weight polymer by combining the mac intermediate with methylene bis(4-phenylisocyanat This low molecular weight polymer is then reacted t ther with hydrazine to give a high molecular weight el tomer polymer in accordance with the disclosure French Patent 1,172,566.

Representative of non-elastomeric binders useful in t invention are polyamides such as polyhexamethylt adipamide, polycaproamide, copolymers of polyhexame ylene adipamide and polycaproamide (preferably /20 copolymer, respectively), poly-N-m ethoxy he methylene adipamide and the like. Representative pc esters useful as binders include polyethylene tere thalate, polyethylene isophthalate, copolymers of pr ethylene terephthalate and polyethylene .isophthal (preferably an 80/20 copolymer, respectively), poly(he hydro-p-xylylene terephthalate), etc. Particularly use polyurethane binders are the polyurethanes formed reacting piperazine and ethylene bis-chloroformate, urethanes of polyhexamethylene adipamide and ethylt bis-chloroformate, etc.

The preparation of nonwoven materials from whr synthetic sheet forming particles is described inlsome. tail in Belgian Patent 564,206. For larger-scale ope tions, it is usually desirable to prepare nonwoven m: rials by a continuous process using, for example, pa; making machinery such as the Fourdrinie r machine 2 other comparable pieces of apparatus. Following pr ration of a waterlcaf of spontaneously elongatable fibers nd binder, the waterlcaf is dried at a temperature low nough to avoid any fusing or melting of the hinder or longation of the fibers. Drying of the waterleaf at from C. to about 140 C. is generally suitable and drying n the range 100 C. to 120 C. is preferred.

As indicated previously, nonwoven webs suitable for [SE in the process of this invention can also be made using arding machines, Rando-Webber machines or other :quivalent devices, or by the process of Belgian Patent $08,646. That patent describes a process in which a runting multifilament bundle of continuous synthetic organic ilaments is charged electrostatically in such a manner as 0 separate each filament from adjacent filaments and hese are thereafter collected to form a nonwoven web.

After formation of the web by any of the abovelescribed methods, it is then heated to elongate the fibers and fuse the binder to the fibers at their cross-over points .vhile restraining the fabric from enlarging substantially n surface area. Sufiicient restraint should be applied to prevent more than 3% increase in linear growth of the fabric in any direction. This ispreferably accomplished by pressing the web between two screens or similar foramlnous members. During pressing, the fibers elongate and :rimp in the thickness direction of the fabric, thereby giving additional bulk to the final product and providing a fabric-like hand due to the bulk thus attained and due to the pattern thus embossed on the fabric by the screen or other foraminous member. Restraint may be applied by other means, however, such as pressing between two flat or curved surfaces, whereby surface friction provides sufficient restraint. Equally well, a curved surface and a screen may be employed, as well as other techniques known in the art of shaping, vacuum forming, etc. Another useful technique is to press the web between irregular surfaces, such as, for example, sandpaper, and thereby obtain a creped surface. By using a combination of an irregular surface with another restraining surface, other unusual designs or patterns can be obtained. For example, a combination of sandpaper and screen surfaces leads to a patterned crepe.

Still another means of providing restraint is to add a small amount of non-self-elongating fiber to the web. Thus the presence of up to about of conventional fibers whether of the shrinking (at processing conditions) or non-shrinking variety may provide the necessary restraint without the use of other external restraining means as mentioned above.

Elongation of the fibers in the web is usually achieved by heating the dry web at 150 C. to 250 C. for a few minutes, usually less than 10 minutes. It is essential that some fusing (bonding of the fibers) of the binder occurs before all of the desired amount of elongation of the fibers is completed, and likewise it is essential that some elongations occurs before all the desired amount of bonding is completed. Preferably, both elongation and bonding take place simultaneously, and this is easily achieved by choice of a suitable temperature dependent upon the compositions of binder and fibers. Usually, pressing the web at a temperature between 150 C. and 220 C. will sufiice. Naturally, the precise degree of fusion and amount of elongation will depend upon the temperature and time of pressing and pressure used. Under extreme conditions of pressing when a fibrid binder is present, the fibrid particle identity is lost and the fibrids become fused completely into the nonwoven structure.

In the production of the preferred nonwoven fabrics already described, the embossing procedure offers a valuable improvement in the woven-like characteristics which are desired. For example, when pressing between screens is employed, the self-elongatable fibers elongate and assume a third-dimensional configuration on the surface of the fabric due to penetration of portions of the fibers into the interstices of the screen. Such configuration gives desirable bulk to the fabric. Similar response to other preferred embossing techniques is also possible, and such thirdalimensional configurations make an important contribution to the suppleness and drapability of the products obtained thereby. In general, to obtain products of greatest interest, it is usually found that a moderate degree of pressing is most satisfactory.

Drapability is measured by determining the length of fabric which is necessary to cause the fabric to bend from the horizontal plane when under no constraint to such an extent as to contact a declining angle of 41.5 of slope from the point of departure of contact. A strip of fabric one inch wide is placed upon a block of wood or other horizontal surface. Abutting the horizontal surface of this material is a 41.5" inclined plane, which at its top adjoins the horizontal surface. The test specimen is placed with the narrow edge at the juncture of the horizontal and the inclined surfaces. It is then moved forward over the inclined surface until the free end touches the 41.5 slope of the testing block. The drape stiffness, designated C," is measured in inches, being one-half of the free length of specimen extending beyond the horizontal surface edge. An equivalent test, the cantilever test of ASTM D 1388-55T, gives values in the range of 50 to 2,000 mg.-cm., in measuring the stiffness of fabrics.

Bulk of a fabric is determined by cutting a square portion of the fabric of uniform thickness, measuring its dimensions, including its thickness, and then calculating its volume. The fabric sample is measured for thickness by means of a conventional fabric thickness caliper device such as an Antes gage (manufactured by B. C. Ames Company, Waltham, Mass). With fabrics having an embossed or other irregular surface, more accurate measurements of the thickness can be made by wellknown microscopic techniques. The fabric sample is then weighed and the bulk expressed in terms of volume per unit weight.

Tensile strength is determined on a one-inch strip of fabric in conventional manner employing an Instron Tensile Tester. For purposes of this invention, tensile strength is determined at room temperature under ambient conditions of 65% relative humidity. The ratio of tensile strength of a fabric to its drape-stiffness is useful for comparing the fabrics obtained by the process of this invention with conventional woven fabrics, felts, and

papers.

Sonic velocity-elongation differential is a measurement of the effect of fabric elongation (and tension) on the velocity of sound transmission in the plane of the fabric. Measurement of sound velocity in fabrics is Well known (see article by W. H. Charch, W. W. Mosely in 29 Textile Research Journal, page 525 (1959)) and involves well-established principles and techniques. The velocity of propagation of sound waves in a fabric is dependent on fabric tension and is indicative of certain fabric properties. Woven fabrics, and also the nonwoven fabrics obtained by the process of this invention, provide media through which sound travels at a velocity which is strongly dependent on the elongation (and the tension) in the fabric, indicating that both have very similar structural characteristics and properties despite their vastly different coarse structure (e.g., woven vs. nonwoven). Other materials, such as felts, papers, and leathers, transmit sound at a nearly constant velocity, that is, substantially independent of the degree of elongation of the structure.

Sonic velocity in a fabric can be measured using a piezoelectric crystal signal source (or other source) to provide vibrations of the desired frequency. Frequencies in the range of 1,000 to 40,000 cps. are conveniently employed. As a detector, a search transducer (a piezoelectric crystal is again suitable) is used, placed at a fixed distance from the source. Pulse propagation timing or wavelength measurement are suitably used to determine sonic velocity. For the purposes of measurements employed here, the source and detector can both be placed TABLE I.VELOCITY AT DIFFERENT ELONGA'IIONS Sheet Material 0% 3% 6% Ratio Nylon paper 1.05 Nylon woven fabric. 1. 35 N onwoveu (Ex. 2)- 1. 32

It will be seen that the paper material, while having a high critical sonic velocity value, shows no substantial change as it is tensioned. On the other hand, the woven fabric and the nonwoven fabrics obtained by the process of the present invention show a sonic velocity value which increases by at least 30% when the fabric is elongated 6%.

The preparation of non-woven materials from wholly synthetic sheet forming particles (fibrids) is described in some detail in Belgian Patent 564,206. In that patent it is shown that polymeric materials may be prepared in the form of particles which have the property of interentangling with one another and with staple fiber materials to form strong sheet materials. Such sheets are advantageously prepared by deposition of the fibrid particles from an aqueous slurry onto a screen in laboratory operations. Waterleaves or hand sheets may be prepared on a small scale by pouring a suitable amount of the slurry onto a small rectangular screen and draining the water down through the screen. Such hand-sheet waterleaves are suitable for the practice of the present invention in that they permit a simple, small-scale preparation of nonwoven structures which can then be tested for physical properties, strength, and the like. For larger-scale operations, it is usually desirable to prepare nonwoven materials on a continuous process using, for example, paper making machinery such as the Fourdrinier machine and other comparable pieces of apparatus, as well as carding machines, Rando-Webber machines, and other equivalent devices. It is well established in the papermaking indus tries, which 'base their operations on the use of beaten wood pulp and similar cellulosic materials, that laboratory hand-sheets are satisfactory as small-scale prototype of the continuous products which can be prepared on small-scale papermaking machinery. In the examples below it is shown that both small-scale experimental units of nonwoven fabrics can be prepared in accordance with the teachings of the present invention and that the same operations are applicable when continuous 'papermaking machinery or other sheet and web-forming devices are employed.

Certain of the nonwoven fabrics prepared by the process of this invention are characterized by a high degree of drapability and flexibility, and a desirable level bf loftiness, and handle. Because of these and other properties, the fabrics produced by the process of the invention are well suited to end uses which have heretofore employed woven fabrics of varying weights and weaves. Among such uses may be listed apparel; draperies; upholstery materials; household furnishings, such as table cloths, napkins, and bed linens; shaped articles, such as gloves, head coverings, brassiere cups; fabric stitfeners, such as interliners, peplums, cuff and collar liners, and the like. In the field of apparel fabrics, the fabrics of the present invention are specifically well suited to work and service clothing, sports wear, outer wear, bathing suits, shirts, and the like. Other fabric utilities include foundations for leather-like laminates, backings for vinylcoated upholstery, and other fabrics, automobile and airplane headliners (in this use the embossable nature of the nonwoven fabrics of this invention is particularly desirable) filter cloths and other industrial felts. These fabrics are also suitable with proper coatings or surface treatmentv for use as fuel pump diaphragms, hosing fler ible couplings, and air bellows for use in instrument: tion work and decorative covers for deskequipmen radios, ash trays, cigarette boxes, and the like.

Because of the conformability and bulkability of th fabrics, as well as the thermoplastic nature of the fibI'Ol. materials employed in these products, it ispossible an desirable to shape or form the sheet products of ,th present invention obtaining thereby articles possessin specific and desirable three-dimensional configuration In general, it is preferred that when fibrid binders at used, the products of the present invention be heat-treate to a degree sufficient to fuse at least a portion of the fibri binders. However, non-fused products are also of it terest and have found applications in a number of th utilities indicated above.

As has already been indicated, the nonwoven fabric of the present invention are embossable and can be of tained with any of a wide variety of surface pattern which may be impressed upon the fabric during th pressing or fusing process. Such embossed configu-rz tions not only supply decorative and attractive appeal ance, but can be used to control the physical propertie of the fabric. Thus, an embossing pattern consistin of a number of parallel fine lines in one direction onl produces a fabric which has a greater flexibility in on direction than in the other direction. Embossing wit a cross-hatched type of pattern of fine lines increases th stiffness of the fabric in both directions. Thecrepe structures obtained by restraining the web between i1 regular surfaces exhibit exceptionally good recover after deformation. Other embossing techniques can b used to alter the handle and feel of the fabric-and als to control the receptivity of the fabric to printing, dyi

' ing, and other coloring post-treatments. During th embossing process the bulk of the nonwoven fabric ca be controlled to any desired degree, and compression ca be introduced to lead to a more compact structure, I this is desired. Furthermore, it is not necessary thz only a single embossing step be introduced. If desirei it is possible 'to emboss upon the nonwoven fabric a over-all textured pattern by the use of wire screens as a ready shown. Thereafter, this fabric can be furtht modified by a second embossing treatment employin platens, calenders, intaglio rolls, or the like.

Fabrics obtained by the process of the present inver tion when staple fiber nonwoven webs are used can t buffed to expose surfaces which are densely populate with uniformly distributed fiber ends of equal lengtl Such buffed surfaces are very attractive and resembl to a surprising degree in hand suede leather and. otht similar products.

The products obtained through the practice of th present invention have a number of advantages in con parison to previously known nonwoven fabrics. In con parison with ordinary and conventional cotton or W04 felts, the present materials show equal or higher strengtl greater dimensional stability, and greater flexibility conformability. In comparison with nonwoven shei products from ordinary synthetic fiber' staple bonded-wit resin materials, nonwoven fabrics obtained by the preser invention have a much softer handle, greater strengl and flexibility, and a better dyeability and printabilit In addition, fabrics made by the present invention sho an excellent degree of post-formability, high elongatic and liveliness, excellent wash-wear characteristics, ou

. standing tensile and stitch strength, and, as has-.alread been indicated, a degree of drapability and controllabi handle which has not hitherto been achieved in n01 woven fabrics in the art.

Particularly desirable fabrics of the present. inventic are those prepared from formulations comprising at lea 25% of a fibrid binder prepared from an elastomer polymer, together with at least 50% of a spontaueousl elongatable fiber material having, under the conditior scribed for determination of spontaneous elongation, l elongation of at least Other useful embodiments of the present invention are apable and flexible but somewhat more crisp and firm inwoven fabrics prepared from formulations comprisg at least 75% of a spontaneously elongatable fiber .ving a minimum of 10% spontaneous elongation, to- :ther with a fibrid binder based upon a synthetic pol- :ster polymer to the extent of at least 3 and not over by weight.

Any of the techniques which are known for the prossing of conventional staple fibers in the preparation nonwoven fabrics can be used in the present inven- )1]. For example, it is sometimes desirable to prepare layered type of structure by depositing upon the surface the fabrics of this invention small amounts of addi- Jnal fibrid binder, say in the order of 0.10 oz./sq. yd., order to provide a firmer and more completely bonded rface. Deposition of the binder is followed by fusion, 1d sheets prepared in this way show an improved reiance to surface wearing, marring, fuzzing, pilling, and .e like.

While several of the preferred embodiments of the resent invention employ fairly short staple fibers, that Mi" long or less, it is possible and at times desirable i use longer fibers, including staple fibers as long as three ches. Dispersion and deposition of such fibers into a wet product are made easier by the use of foam-disperon processes or liquids of higher viscosity, rather than 1e water-dispersion processes described in connection with lorter fibers. Other web-forming processes may also be sed. The use of longer fibers or continuous filaments inreases the tensile strength and tear strength of the nonoven materials of this invention.

The following examples illustrate the invention. arts are by weight unless otherwise indicated.

All

Example 1 Three parts self-elongatable poly(ethylene terephthalte) staple fibers ('A long, three denier per filament) repared according to the process of Belgian Patent 566,- 45 and having a spontaneous elongation of 12%, are dmixed by vibration stirring (using a Vibro Mixer) with 000 parts of water. The fibers are pre-wetted with a nall amount of a polyethylene oxide ether fatty alcohol s wetting agent. To this fiber suspension is added a urry containing two parts of the synthetic elastomer brids in 5000 parts Water prepared according to the rocedure of French Patent 1,172,566 by reacting a polytetramethylene ether) glycol of approximately 1,000 mo- :cular weight with tolylene-2,4-diisocyanate to give a lycol-terminated macrointermediate. This is treated to ive an isocyanate-ended, low molecular weight polymer y combining the macrointermediate with methylene is(4-phenylisocyanate). This low molecular weight olymer is then reacted further with hydrazine to give high molecular weight elastomer polymer. This synretic elastomer is soluble in dimethylformamide. A alution is prepared containing 12% synthetic e astomer Jlids and 4% polyvinylchloride solids in dimethylformmide. Fibrids are then prepared according to Belgian 'atent 564,206 by placing 400 ml. of glycerol together rith 0.5 ml. of an organic surfactant in a one quart Warig Blendor and adding the polymer solution while runing the Blendor at full speed. The glycerol precipitates 1e polymer from solution, and the Waring Blendor sub- :cts the precipitating polymer to high shear to give elastoieric fibrids. The washed fibrids are stirred for a few econds in water to break up agglomerates, and the fibrids nus obtained are then maintained in water suspension eady for use. This stock is poured into a head box of sheet mold, and a waterleaf is deposited onto an 8" by IOO-mcsh screen. The screen with the deposited water- :af is removed from the sheet mold and placed between bsorbent cloths and rolled with a steel rolling pin to Percent Tongue Fibrids/ Tensile Tear Drap- Comments percent Strength Strength ability Fibers 20180.. Fair Poor Good. Strength too low. 25/75.. do Good ..d Borderline. 40/60 Excellent Excellent Excellent Best combination. 50/50 ..do Good Good Adequate. 70/30 Good.-. Poor Poor Unsatisfactory.

From these results, it may be seen that when elastomer fibrids are used as the binder for the nonwoven sheets of this invention, a minimum of 25% of such fibrids is needed, while anything over 50% fibrids gives less desirable sheets. Also, a minimum of 50% self-elongatable fibers is needed for soft, drapable fabrics. Using other elastomer fibrids, similar results are obtained.

Example 2 A 46% solids dispersion of a polymeric acrylate ester elastomer containing 92% ethyl acrylate, 6% methyl acrylate and 2% acrylic acid is converted to highly stable fibrids as follows:

To a quantity of the dispersion sutficient to contain parts of elastomer is added 5 parts of diepoxide resin, :1 monomeric bis-glycidyl ether of diphenylol propane having an epoxy equivalent of 175-210 (Epon 828, sold by Shell Chemical Corporation) and 5 parts of hutylated melamine formaldehyde resin containing one part melamine to 4-5 parts formaldehyde (Uformite MM-46, sold by Rohm and Haas Company) and 5 parts of titanium dioxide pigment.

The compounded mixture is converted to fibrids by adding the resin blend to a Waring Blendor containing a 5% solution of sodium sulfate in hot water (75 C.) with 0.01% of an organic quaternary ammonium ,salt as wetting agent. The Blendor is operated at full speed during the addition. The resulting fibrids are used'in the form of the slurry thus prepared.

The staple fibers employed are similar to those of Ex ample l with a spontaneous elongation of 10% when immersed in boiling water for 5 minutes.

A slurry of 3 parts of the above fibers with 2 parts of fibrids, in 10,000 parts of water, is prepared as in Example 3 and a waterleaf is prepared in the manner of Example 3 also. The sheet is removed from the screen, placed between 21 cotton cloth sheet and a l2-mesh wire screen, and dried at C. for 3 minutes. The dried sheet is then placed between 50-mesh screens and embossed and bonded by pressing at 205 C. for one minute at 200 p.s.i. The sheet is further cured by exposing to air at C. for 5 minutes and then washed and tumble dried before testing. The fabric has a tensile strength of 5.9 lbs./in./oz./yd. a drape stiffness of 0.75 inch, and a wet tensile strength of 4.5 lbs./in./oz./yd The fabric is found to have good strength retention when exposed to drycleaning solvents. The embossing treatment produces a fabric resembling Oxford cloth in appearance, with excellent whiteness, good rctcntion of whiteness under laundering and pressing, medium porosity, and good handle.

During the process of curing and embossing, the sheet can be conformed, if desired, to a three-dimensional shape, of the fiat sheet.

The compounded elastomeric mixture of Example 2 is used in this example without conversion into fibrids. The self-elongatable fibers are also the same.

The fibers are formed into a web by slurrying in water using a conventional fiber wetting agent and forming a waterleaf. The waterleaf is air-dried on the screen, since it cannot be handled unsupported.

The elastomeric mixture of Example 2 diluted with an equal volume of aqueous sodium sulfate solution, is used as a dip-bath. The waterleaf on the screen is immersed in the dispersion and excess bath is removed by blotting. The impregnated watcrleaf is placed in an oven at 160 C. with air circulation for 3 minutes, and theresin is coagulated by the action of the salt and the heat.

The waterleaf is removed and placed between 50-mesh screens and treated as in Example 5. The resulting sheet, which has the appearance of Oxford cloth, is composed of 60% fibers and 40% resin binder by weight. This sheet, while equivalent to the fibrid-bonded sheet in physical strength properties, is somewhat more porous and has a lower covering power.

In a similar manner, a solution of the compounded resin of Example 5 is prepared by adding acetone to make a 4.5% solids solution. The unbonded waterleaf is immersed in this solution, the excess solution is drained off, and the impregnated waterleaf is placed in a pan of hot water (75 C.). This precipitates the resin and causes bonding. Then the sheet is dried on a sheet drier and is embossed and bonded and cured as in Example 2. The resulting sheet is equivalent to the fibrid-bonded structure in all physical properties.

Example 4 A variety of synthetic elastomer resins are formed into fibrids by the procedure of Example 2. Table II shows the results obtained by making nonwoven fabrics employing 40% of these fibrids as binders, with 60% of the self-elongatable fibers of Example 1, using the procedure of Example 2.

A suspension of fibers is prepared by combining 10,000 parts of water with 3 parts of A" long, 3 denier per filament self-elongatable polyester fibers of Example 1 (but having a spontaneous elongation of thoroughly wetted with a 5% solution of polyethylene oxide ether fatty alcohol surface active agent (Alkanol HC). To this suspension of fibers is added a sufficient portion of a slurry of 45/55 butadiene/ styrene elastomer fibrids to provide 2 parts of fibrids in suspension form. These fibrids are prepared by combining a 45/55 butadiene/styrene polymer in the form of a 56% solids dispersion in water with compounding agents as follows: 5 parts of finely divided pigment grade Rutile titanium dioxide; 5 parts of zinc oxide; and 2 parts of Antioxidant 425, an antioxidant sold by American Cyanamid. This is dispersed with 12 parts of water to give a 50% solids dispersion. This is added to 100 parts of the butadiene-styrene polymer in a 14- 56% solids dispersion in water. From this compoimdec resin dispersion fibrids are prepared by shear pnecipita tion and coagulation. The coagulating system consist: of a solution of 400 parts of water containing 0.31 par of aluminumsulfate (Al- (SO -18H O), 0.31 part 0 sulfuric acid and a small amount of organic surfactan (Triton X-100) wetting agent. A Waring Blendor is se to operate at low speed, and to the slowly stirred systen is added a fine even stream of the compounded polyme: dispersion described above. Suficien t quantity of tht dispersion is added to be equivalent in volume terms t( Il /2% 0f the coagulation solution. After all the disper sion has been added, the system is allowed to stir for at additional two minutes to allow the binder particles tr coagulate thoroughly to avoid agglomeration. The poly mer from this reaction is obtained in the form of fibrid slurry suitable directly for use in .the preparatioi of a waterleaf.

This fiber-binder suspension is then poured into 2 headbox of a sheet mold, and a waterleaf is depositez onto an 8" 8" 100-mesh screen. Excess water i: squeezed from the waterleaf by placing it while still or a 100-mesh screen between absorbent cloths and rollin it with a steel rolling pin. The waterleaf is then remover from the screen and placed between SO-mesh screens which in turn are placed between sheets of pulp boar; and dried in a press at 150 C. and lbs/sq. in. pres sure for 10 minutes. Following this pressing treatment the nonwoven sheet is obtained in the form of a fabril having a woven texture due to the imprint of the mesh screen and the 50-mesh screen which had been ii contact with it during pressing. The sheet is'tested 'fo. physical properties and found to have a tensile strength 0. 3.12 lbs.' /in./oz./sq. yd. and a tongue tear strength 0 1.01 lbs./oz./sq. yd. The drape stiffness in inches 0 the sheet is 0.796. It is observed that washing this shee in a synthetic detergent followed by drying at 80 C. in creases its strength as follows: tensile strength of 5.2. lbs./in./oz./sq. yd.; tongue tear strength of 1.16 lbs/oz. sq. yd. The drape stiffness is decreased slightly to 0.722 inch.

Example 6 A number of fabrics are prepared in accordance wit] the procedures of Example 5 in different fabricweight for evaluation as apparel fabrics. The first ofj'these i prepared with a weight of 2.5 oz./sq. yd. and is of weight and handle indicating suitability fora shirtin, fabric. A sheet 5 feet long and 28 inches wide of thi deposited waterleat' from a Fourdrinier machine is-placer between 60-mesh screen sheets which are in turn mounte on stainless steel plates and placed between the platens o a press and held there for 5 minutes at C. and 13. lbs/sq. in. pressure. The pressed piece obtained in thi manner has a distinct weave pattern resembling Oxforr cloth. This fabric, which sews readily, is converted int: dress skirts.

A second fabric with a weight of 3.5 oz./sq. yd. is als prepared. This fabric is of a weight suitable for 'us as dress goods. As before, the fabric is embossed betweei 60-mesh screens mounted on stainless steel plates: '-Th1 white fabric, after pressing, is evaluated for screen-pig merit printing. A pattern is applied with four difi'eren colors: orange, yellow, black, and olive. The printer fabric is cured for 15 minutes at 350 F. The pattern i sharp and the colors bright. Two dresses and two skirt are prepared from the printed material, and in additioi a skirt is prepared from a separate portion of the fabrir without printing, but dyed a red color with a disperser dye.

A third fabric, weight 4.5 ozs./sq. yd., is prepared a above, except that 50-mesh screens are used instead 0 60-mesh. This fabric is embossed in the same manner a before and then dyed with a tan dispersed dye. This ma terial is used to make a wind breaker jacket and a pai of trousers. A separate portion of the same material i reen printed with five colors, red, green, turquoise, gray, id black, to give a floral design.

A fourth fabric is prepared, fabric weight 5.5 ozs./ sq. l., and this fabric is screen printed without previous nbossing. The printed fabric is then cut into pieces and nbossed between 24-mesh screens mounted on stainless eel plates in a press at 140 C. and 135 lbs/sq. in. for minutes. The pressed fabric is 'boiled off in an aqueous rlution of a synthetic detergent, dried, brushed slightly, reared and semi-decated.

In general, it is found that all of these fabrics, through .e wide range of. different weights, can be handled as .dicated in normal textile processing steps similar to 1056 employed on woven fabrics. The non-woven fabcs which are obtained are dyeable as indicated, can be :wn, and in every way are equivalent to satisfactory oven fabrics, even though as already indicated they conin no woven material.

Examples 7-23 Table III illustrates the advantages of the present invenon and compares the fabrics produced with other nonoven fabrics and also with conventional woven fabrics. .comparison of Examples 10 and 17 of Table III shows tat; compared to the product of this invention, selfonigation and development of crimp prior to web fonnaon give a relatively inferior product.

fibrids are filtered and washed with water until free of organic liquids. 3

A nonwoven fabric is prepared from a formulation comprising selfelongatable fbers of the type described in Example 1, together with fibrids as described in Example 24 using the procedure of Example 5. Because a highly efiicient bonding is realized in this sheet, a low proportion of binder gives very satisfactory results. A sheet is prepared from 92.5% of the spontaneously elongatable fibers and 7.5% of the copolyester fibrids. After formation of the waterleaf, the fabric is dried at 130 C. between screens under a pressure of 50 p.s.i. and then fused between the same screens at 190 C. and 10 p.s.i. pressure. The sheet so prepared has a weight of 3.1 0zs./yd. a thickness of about 18 mils, a tensile strength of about 8.0 lbs./in./oz./yd. and a firm but flexible handle, rendering it suitable for use as a suiting intcrliner.

Other sheets are prepared, using the same fibrids and the same fibers, but in different proportions. It is found that when the amount of these hard (nonelastomeric) polyester fibrids is decreased to 2% or less, there is not sufficient binding action to provide a strong sheet. When the content of these fibrids is above about 25%, the sheets are very strong, but flexibility and drapability decrease. When as much as 50% of these polyester fibrids are used, the sheet becomes stiff and papery, even when optimum finishing treatment is employed. Similar TABLE III.COMPARISON OF WOVEN FABRICS WITH NON-WOVEN FABRICS 01 THIS INVENTION Fabric Properties Tensile I Basic wt. Thlck- Density strength Drape Tensile, Ex. Fabric type Composition (0z./yd. ness (g./cm. (lbs./in.l stifiness drape Appearance N0. (mils) ozJydfi) (inches) (1135.)

Cotton broadcloth. 100% woven cotton--. 3. 80 10.0 0. 59 12. 5 0.91 45 Typical woven fabric. Cotton twill d0 8.5 21.0 0. 63 10.0 0. 92 91 D0. Wool flannel- 100% woven wool"--. 8. 0 34. 0 0. 37 3.6 0. 62 36 Do. I.--" Nonwoven iibrid 00% 8.13. Fiber AA 3 5 14. 0 0. 40 5. 5 0. 75 26 Very similar to woven bonded. 40% Fibrid B! fabric; good covering power. ..do 5. 7 17. 0 0. 53 6. 2 0.97 38 Like woven fabric.

00% 8.12. Fiber 0, 3.5 13.0 0.42 4. 2 0. 75 20 D0.

40% Fibrid B. 95% 8.13. Fiber A, 5% 3. 5 19. 0 0. 28 3. 4 0. 97 12 Between v oven fabrics Fibrid D. and lelts. t N onwoven resin 60% 8.13. Fiber A, 3. 6 14. 0 0.41 6.7 0.80 More port) 15 than fibridbonded. 40% acryiate terbonded fabric:

polymer. good properties. i do do 5 3. 6 14. 0 0. 41 5. 7 0. S0 26 Like woven fabric. i Commercial W001 100% wool fibers 5. 5 39. 0 0. l8 7. 5 1. .18 32 Typi gal felt: bulky and e t. sti Nonwoven fibrid 60% modified Fiber 3. 3 11. 0 0. 47 4. 1 1. 14 12 Papery; too stiff.

bon e 11, 40% Fibrid B. t do 60% "Dacron" staple, 3. 5 9. 5 0.58 5.1 1. 56 11 Do.

40% Fibrid B. t do 00% crimped "Dnc- 3. 3 10.0 0. 52 4. 4 1. 10 Do.

mm, 40% Fibrid B. L. Commercial non- Pellon 920" (synthct- 2. 6 20. 0 0.16 3. 4 1. 64 5 Very stiff and bulky.

woven. .do Chicopce "Lustron 2. 3 10.0 0. 36 7. 0 1. 45 11 Stiff and papery.

drapery. E do "Pellon Polkn-dot" 2. 7 11.0 0. 38 6. 7 2. G5 7 Very stiff. i do Clgicgpee Mills Key- 2.6 12.0 0.34 3.3 E 3.0 3 Do.

1 $.15. Fiber .1, self-elongatable polytcthyleue terephthalntc) bers of Example 1.

2 Flbrld B, fibrids prepared from an elastomeric terpolymer ased on ethyl acrylutc as described in Example 5.

3 8.15. Fiber C, selfielongatable polyamide fibers of Exmple 25.

4 Fibrid D, fibrids of Example 24.

Example 24 Elastoiner of Example 5 added as a dispersion in water (not as fibrid).

" Elastomcr added as a solution obtained by adding an equal volume of acetone to dispersion (5).

Modified SJ). Fiber A obtained by elongating $.15. Fiber A in bulk form prior to use. This gives a crimped staple fiber with no residual spontaneous elongation.

SADOVG.

fabricscan be made on a continuous basis on a Fourdrinier machine.

Example 25 A polyarnide is prepared by melt polymerization from para-xylylene diamine and azelaic acid by conventional procedures. The polymer is then melt spun to give continuous polyarnide filaments which are used to prepare spontaneously elongatable fibers. The spun filaments are drawn 3X at room temperature after being wetted with water and then relaxed in a C. water bath to shrink them 45% of their drawn length.

The filaments are then cut into staple lengths and are found to have a spontaneous elongation of 7% when immersed in 100 C. water for minutes. A non-woven fabric is prepared using 60% of these staple fibers (/4 lengths) and 40% of fibrids of Example 1 according to the procedure of Example 2. The sheet is dried on a screen in an oven at 120 C. giving a soft, drapable fabric with good handle.

Example 26 Sheets are prepared from poly(ethylene terephthalate) using the apparatusshown in FIGURE 5 of' Belgian Patent 608,646 granted October 13, 1961. Referring to that drawing, filaments 1 spun from spinrieret I. pass in the manner shown over the bar guides 3, 4, and 5, thence to aspirating jet 6 supplied with air under pressure through inlet 7. Aspira'ting jet 6 embodies extended filament passageway extension 8 flared outwardly (6) at the terminus 9. The charged filaments 10, which separate on exiting the extension of jet 6, are collected on receiver 11, an aluminum plate. The various components downstream from spinneret 2 are grounded through leads 12. The pertinent distances along the filament line are as follows:

a=13 inches e=ca. 4 inches b=17 inches f=48 inches c=20 inches g=7 /z inches d=23 inches h=12 inches The filaments are quenched with air, applied 6 inches below the spinneret face. The guide bars 3, 4, and 5 are 1" x 1" with rounded edges and are composed of chromic oxide. Guide bar 4, i.e., the functional surface thereof, is offset from the filament line by 2 inches. The entire jet assembly is fabricated from brass.

' In operation, poly(ethylene-terephthalate) (34 relative ,viscosity) is spun through a 30-hole spinneret at a rate of grams (total) polymer per minute. Each spinneret hole is 0.007 inch in diameter. The spinning tem- In all of the runs reported in Table IV, process operability is good, as is sheet formation. The resulting sheets are substantially free from aggregated filaments, i.e., filament separation subsequent to charging is wholly satisfactory. Note that increasing air pressure results in a corresponding increase in the speed at which the filaments are delivered to the receiver; filament speeds increase from ca. 2000 yards per minute in run 1 to ca. 3540 yards per minute in run 6.

In each of the above runs, atmospheric steam at about 150 C. is applied to the separated filaments downstream from the aspirating jets, using a foraminous member disposed annularly with respect to the filaments, the filaments relax upwards to or more with concomitant development of crimp. Upon later calendering, the filaments in the sheet elongate spontaneously, thereby further contributing to the crimp level in the individual filaments and hence to the properties of the sheet.

When each of the above runs is repeated excepting that the filaments are collected on a moving belt partially submerged (over the area on which the filaments are collected) in 75 C. water, the filaments again relax leading to the development of crimp up to levels of 5( or more crimps per inch (based on in situ examination) The filaments also spontaneously extend upon subsequen treatment at elevated temperatures.

The filaments also may be caused to relax by employ ing a heated gas in the aspirating jet. In one such run air at p.s.i.g. and 120 C. was employed, leading tr results similar to those described in the foregoing.

By repeating this example, excepting that 2 or 3 fila ments by-pass the guide bars 3, 4, and 5 without con tacting them, and such filaments emanate from a separate jet and are forwarded at a lower speed, a sheet is collectec which contains these less oriented filaments disperser throughout as a binder fiber. Subsequent heating results in fusion of these filaments, leading to a more coherent sheet.

Continuous filament sheets of this type may be bondec' with fibrids or with resin dispersion as shown in earliei examples. The sheets formed in all cases are equivalent to those obtained using self-elongatable staple fibers and comparable bonding systems. Such sheet products are useful in all aspects of the present invention.

As is shown above, a number of highly desirable and useful nonwoven fabrics can be prepared. in accordance with the present invention. Such nonwoven fabrics vary in fabric weight, fabric density, flexibility, strength, anc handle. However, all of these materials have in common characteristics which suit them to meet the requirements and standards of woven fabrics, although they are, in fact, prepared without weaving operations.

Example 27 Poly(ethylene terephthalate) continuous filaments were spun from a 34 hole spinneret to give a nonwoven wet: of polyester fibers. The web consisted of individually disposed randomly oriented filaments deposited through an air-jet which forwarded the filaments from the spinnercl over a chromic oxide charging bar which caused the generation of a static electrical charge in the individualfibers, in accordance with the teaching of the previous example. The web contained co-spun binder filaments of a copolymer of poly(ethylene isophthalate) and poly(ethylene terephthalate) (20/80 composition) making up 10%, ot the total weight of the web. The homopolymer poly (ethylene terephthalate) was spun under conditions tc give filaments with controlled orientationto give from 25% to 55% shrinkage on treatment with 75 C. water for 1 minute. i

Following web formation, the nonwoven material was shrunk at controlled dimensions (on a tenter frame) to allow an area shrinkage of 50%, by treatment with C. air with residence time of 1 minute. The filaments ol the web were then found to be spontaneously elongatable, the average filament showing an elongation of 1% on treatment with boiling water for 5 minutes. p

The web, after shrinkage, was bonded and the filaments were simultaneously elongated by pressing the webbetween 40 mesh screens at 215 C. for 1 minute with a pressure of 200 p.s.i.

The resulting material was a soft, flexible nonwoven fabric having a textile pattern imposed by the embossing function of the screens. The fabric had a tensile strength of 7.0 lb./in./oz./yd. an elongation of 73%, a drape stiffness of 1.16 inches. I

Similar results were obtained when the web was prepared without binder filamcnts, the bindingaction being provided by application of a dispersion of an elastomeric acrylate terpolymer resin in water to give a binder content of 35% by Weight based on the total fabric. The binder was applied to the web prior to shrinkage, and the final bonding action was completed by heatingwhich' simul taneously caused spontaneous elongation as before. This latter fabric had a tensile strength of 7.4 lb./in./oz./yd. an elongation of 79%, and a drape stiffness of 0.9.5 ,inch.

19 Example 28 Example 29 A random web was bonded as in Example 28 except that one of the 30 mesh sandpaper sheets was replaced by 80 mesh sandpaper. The resulting product was similar to that in Example 28, except that the crepe appeared only on the side in contact with the coarse sandpaper. The other side was smooth and therefore readily adaptable to coating for coated fabric applications, for example, as a vinyl upholstery material.

Example 30 A sheet produced on a triwire paper machine and having a basis weight of 2.5 oz./yd. was bulked and bonded on a drum heated at temperatures of between 180 to 225 C. The sheet prior to the heat treatment was composed of 65% self-elongatable poly(ethylene terephthalate) staple fibers, 25% goat hair and 10% fibrid and was.

prepared in a manner similar to that described in Example l. The poly(ethylene terephthalate) fibers were elongated successfully to give drape, softness and bulk without the formation of surface pucker, wrinkling or other distortion. Without the goat hair, similar sheets showed substantial area shrinkages, developed no bulk, became stiff and showed a puckered and distorted appearance.

In similar experiments using the same self-elongate.- ble poly(ethylene terephthalate) staple fibers but varying the restraining fiber, comparable results were obtained. Thus, an initial sheet containing 88% of the self-elongatable staple, 2% of 3 denier, poly(ethylene terephthalate) staple that shrinks under the influence of heat and 10% of the same fibrid as above, exhibited good bulk development and n area change upon heating for minutes at 210 C. in the absence of mechanical restraint. Small amounts of nylon staple can also achieve the restraining effects when used in the self-elongatablefibridrestraining fiber combination.

What is claimed is:

1. A process for preparing a nonwoven fabric which comprises (a) forming a nonwoven web of synthetic organic fibers and a synthetic organic polymer binder, the fibers being capable of elongating spontaneously at least 3% upon being heated at a temperature 30 C. above the fiber polymer second order transition temperature for five minutes, the binder having an initial modulus of between 0.002 and about 25 grams per denier, and (b) heating the web at a temperature sufiicient to fuse the binder and also elongate the fibers at least 3% while restraining the fabric from increasing more than 3% in linear growth along the surface of the fabric.

2. The process of claim 1 wherein the synthetic organic fibers are polyester fibers.

3. The process of claim 2 wherein the polyester fibers 20 are continuous filaments of poly(ethylene terephthalate). 4.1The process of claim 3 wherein the binder is in the form of continuous filaments of a polyester having a melting temperature at least 20 C. below the melting temperature of said polyester fibers.

5. The process of claim 2 wherein the fibers are staple fibers.

6. The process of claim 5 wherein the fibers are poly (ethylene terephthalate).

7. The process of claim 6 wherein the binder is in the form of fibrids.

8. The process of claim 7 wherein the binder fibrids are composed of a synthetic organic elastomeric polymer having an initial modulus, measured in fiber form, of less than 0.9 g.p.d.

9. The process of claim 8 wherein the binder is a copolymer of an aliphatic ester of acrylic acid and up to 5% acrylic acid.

10. A process for preparing a nonwoven fabric which comprises (1) preparing a suspension of synthetic organic staple fibers and a synthetic organic binder in an inert liquid, the suspension containing less than about 10% solids by weight, the fibers being capable of elongating spontaneously at least 3% upon being heated at a ternperature 30 C. above the fiber polymer second order transition temperature for five minutes, the binder having an initial tensile modulus (Mi) of between about 0.002 and about 25 g.p.d. and being present in an amount, based on total solids such that percent binder X /Mi (binder) 40 (2) preparing a waterleaf from the suspension; (3) drying the waterleaf at a temperature below that at which the fibers elongate spontaneously and also below the fusing temperature of the binder; and then heating the waterleaf at a temperature sufiicient to fuse the binder and also elongate the fibers at least 3%, while restraining the fabric from increasing more than 3% in linear growth in any surface direction.

11. The process of claim 10 in which the fibers are polyester fibers.

12. The process of claim 10 in which the binder comprises fibrids.

13. The process of claim 12 in which the binder comprises elastomeric fibrids.

14. The process of claim 12 in which the heating step is carried out while the fabric is pressed between embossing surfaces to impart a woven-fabric appearance to the fabric surface.

References Cited by the Examiner UNITED STATES PATENTS 2,765,247 10/1956 Graham 162-l 57 2,999,788 9/ 1961 Morgan l62146 3,032,465 5/1962 Selke 162-146 3,049,466 8/1962 Erlich 162-157 3,080,271 3/1963 Quehl 162--146 3,101,294 10/1963 Fridrichsen 162-146 3,117,056 1/1964 Katz 161-181 FOREIGN PATENTS 566,145 9/ 1958 Belgium.

DONALL H. SYLVESTER, Primary Examiner.

HOWARD R. CAIN E, Assistant Examiner. 

1. A PROCESS FOR PREPARING A NONWOVEN FABRIC WHICH COMPRISES (A) FORMING A NONWOVEN WEB OF SYNTHETIC ORGANIC FIBERS AND A SYNTHETIC ORGANIC POLYMER BINDER, THE FIBERS BEING CAPABLE OF ENLONGATING SPONTANEOUSLY AT LEAST 3% UPON BEING HEATED AT A TEMPERATURE 30* C. ABOVE THE FIBER POLYMER SECOND ORDER TRANSITION TEMPERATURE FOR FIVE MINUTES, THE BINDER HAVING AN INITIL MODULUS OF BETWEEN 0.002 AND ABOUT 25 GRAMS PER DENIER, AND (B) HEATING THE WEB AT A TEMPERATURE SUFFICIENT TO FUSE THE BINDER AND ALSO ENLONGATE THE FIBERS AT LEAST 3% WHILE RESTRAINING THE FRIBERIC FROM INCREASING MORE THAN 3% IN LINEAR GROWTH ALONG THE SURFACE OF THE FABRIC. 